The present invention relates to collapsible prosthetic valves for use in heart valve repair. More particularly, the invention relates to methods and apparatus used to deploy balloon-expandable prosthetic valves.
Damaged or weak heart valves may require replacement with prosthetic valves. While prosthetic valves typically have been implanted using surgical procedures, recent developments in this area have led to prosthetic valves which are capable of implantation using minimally invasive techniques. One such technique employs valves supported by stents. Such valves may typically be collapsed into a compressed state for transluminal delivery to the desired location and then expanded in vivo for final placement. Devices for delivering these valves, such as catheter-based delivery devices, may be used to insert the valve through a body lumen of a human or animal, position the valve, release the valve within the body lumen, and, where necessary, expand the diameter of the valve to hold it in place in the body lumen.
Prosthetic valves may be self-expanding or may employ some other method, such as the application of heat or the inflation of one or more balloons, to facilitate expansion. Balloon expansion employs a catheter having a balloon which is inflated to expand the valve into the non-compressed state. Such balloons may be inflated by various methods, including providing gases or liquids to fill the interior space of the balloon. The balloon may subsequently be deflated to release the valve and to enable the balloon catheter to be withdrawn from the body.
In a typical balloon inflation arrangement, a prosthetic valve may be assembled over the uninflated balloon of a balloon catheter and then collapsed to a relatively small diameter, or may be slid over the uninflated balloon while collapsed to the relatively small diameter. A sheath of the catheter may then be positioned over the valve to hold it in place and maintain it in the collapsed condition. Once the catheter has been positioned at the desired location, the sheath may be removed, revealing the uninflated balloon and collapsed valve. The balloon may subsequently be inflated to expand the valve stent into contact with the body lumen. Once the valve has been properly placed and the valve stent fully expanded, the balloon may be deflated and the delivery catheter removed from the patient.
After removal of the sheath and prior to inflation of the balloon, several factors may make accurate positioning of the valve within the body lumen difficult. In particular, forces, such as the vibrations of a beating heart and the high velocity of blood flow within and immediately adjacent to the heart, create a turbulent environment which could cause the valve to move relative to the balloon during this time period. For example, the aforementioned forces may increase the likelihood that the valve will move longitudinally along the balloon. It will be appreciated that accurate location and expansion of the prosthetic valve is critical to the proper functioning of the valve. For example, if the valve were to move longintudinally relative to the balloon prior to balloon inflation, the valve may not be positioned in the correct location within the body lumen. Further, if the valve were to move so that the full length of the valve stent does not overlie the balloon when the balloon is inflated, the full length of the valve stent may not be expanded and the valve may not be securely held in place. Therefore, there exists a need for a device which will accurately maintain the position of the valve relative to the balloon during the deployment process.